Maurice Morel-Lavallée first described a unique posttraumatic superficial fluid collection in a patient as a result of a fall in 1863 (38). Later Letournel and Judet (27) coined the eponymous term Morel-Levallée lesion (MLL). Other terms, such as closed internal degloving injury, Morel-Lavallée effusion, hematoma, posttraumatic cyst, and chronic expanding hematoma, have been used in the literature to describe similar lesions (2,13,33).
MLL occurs as the result of direct forces of pressure and shear stress between the subcutaneous tissue and the superficial fascia (2,6,13,28,36,43). The potential space between these tissues is subsequently filled with serosanguinous fluid, blood, and necrotic fat (2,13). Classic history includes crush injury, with soft fluctuant area appreciable on physical exam. In some cases the history of a major trauma is absent (2,34,39). The literature has described MLL in a variety of sports at all levels. The majority have involved the knee, resulting from shearing forces caused by falls on the mat in wrestling or impact with the field in soccer, frisbee, and professional footall (3,8,45,48). The natural course is not well understood; the lesion may increase in size, remain stable, or self-resolve. In some cases, it may recur (2,13).
MLL often occur as a result of motor vehicle accidents; however, these lesions have been described in many different sports (Table) (1,3,7–11,18,20,21,26,31,37,39,45,48,50,53). MLL are rare entities that are difficult to diagnose, making their exact incidence difficult to ascertain. Letournel and Judet (27) reported an 8.3% incidence of MLL in greater trochanteric trauma, and Tseng and Tornetta (49) reported an incidence of 1.7% of MLL in association with patients with pelvic fractures. However, MLL can occur in multiple areas of the body and are not always associated with fractures, making their incidence likely much higher. It is very likely that MLL is not well recognized in sports, and it is underreported.
The clinical presentation of MLL can be explained by the mechanism of injury: a shearing force causes separation of the superficial fascia from the underlying deep fascia, severing blood and lymphatic vessels and nerves that typically cross both planes. As a result of this mechanism, common complaints from patients include pain, a palpable fluctuant collection (consisting of blood, lymph, fat or a combination) over the injured area (Fig. 1), and hypoesthesia that occurs from the shearing of cutaneous nerves during the initial injury and perhaps stretching of the cutaneous and subcutaneous tissues. Many patients with subacute and chronic presentations may not complain of pain (2,13,20,23,24,28,32,39,52). The fluid that collects is susceptible to infection, and thus infections of MLL represent real and important sequelae.
MLL have been reported in various parts of the body. In a literature review, Vanhegan et al. (51) reported on the most commonly associated lesion sites based on 204 case reports. The greater trochanter/hip (30.4%), thigh (20.1%), and pelvis (18.6%) account for more than 69.1% of the documented cases of MLL (51). The knee accounts for 15.7% with the remainder of cases occurring in the gluteal (6.4%), lumbosacral (3.4%), abdominal (1.5%), calf/lower leg (1.5%), and head regions (0.5%). Interestingly, our literature review revealed that the knee was the most commonly reported site in sports-related MLL (Table 1). The site of injury can affect the presentation, especially in athletes who depend on mobility.
Presenting complaints can be variable but often include a fluctuant mass, hypoesthesia and in certain cases, limited mobility depending on the site of injury. Tejwani et al. (48) explored 27 cases of MLL of the knee that occurred in the National Football League. Common clinical complaints in the 27 cases include: tightness in the anterior thigh with knee flexion to 90 degrees (100%), limited flexion at the knee (41% of cases), and varying degrees of complaints of fluctuant mass, knee and thigh pain, swelling, and ecchymoses (48). Regardless of the mechanism, MLL typically develop within hours or days after trauma, although chronic lesions can occur (2). Up to one third of patients may present months to years later (18).
In sports, the mechanism of injury often occurs from direct contact with the field or surface (Table 1). A sample of 14 case reports of MLL that occurred in athletes revealed 45 players with identified MLL, of which 33 (73%) resulted from direct contact with the field, and seven (16%) resulted from direct contact with another athlete (1,3,8–11,20,26,37,39,48,50). The remainder of lesions were not specified. A careful history of the mechanism of injury can help identify patients who may be at risk of MLL.
Diagnosis of an MLL can be made by careful history and thorough physical examination. Differential diagnosis includes coagulopathy-related hematomas, bursitis, abscesses, fat necrosis, pseudolipoma, and soft tissue sarcomas, particularly in chronic cases (2,8,34,40). Standard radiographs can be obtained initially to rule out bony involvement, specifically an underlying fracture. In the emergency room setting, computed tomography is often used in evaluation of patients involved in significant trauma. Due to excellent soft tissue contrast, magnetic resonance imaging (MRI) has been considered the modality of choice for delineation of the lesion, allowing determination of lesion characteristics and chronicity (2,12,13,34,39). This can be determined through the age and amount of blood, fat, and lymph tissue within the MLL (2,3,13,20). Acute lesions will appear hypointense on T1-weighted images and hyperintense on T2-weighted images (34). As the hematoma organizes, deoxyhemoglobin is converted into methemoglobin which will appear hyperintense on T1-weighted and T2-weighted images (2,3,34). In more chronic lesions, the coexistence of hemosiderin deposition, granulation tissue, necrotic debris, fibrin, and blood clots show intermediate signal on T1-weighted images and heterogeneous hyperintensity on T2-weighted images (2,3,34). A peripheral fibrous capsule will appear hypointense on T1-weighted and T2-weighted images (3,34). A classification system was developed in 2005 by Mellado and Bencardino (34). It consists of six types of MLL based on morphology, presence or absence of capsule, signal behavior, and enhancement pattern (34). Ultrasound (US) offers many advantages as a diagnostic and therapeutic modality. It is dynamic and provides better soft tissue visualization than plain imaging and can be performed in the office unlike an MRI which is ideal for monitoring (6,12,40,51). US imaging shows hypoechoic to anechoic fluid collections between the deep fat and the overlying fascia (6,12,40,51). Acute and subacute lesions are usually heterogeneous in appearance with irregular margins and lobular shape (2,12,40). Chronic lesions may progress to homogenous appearance with smooth margins and a flat or fusiform shape (2,12,40). In the absence of a US machine, aspiration of lesions with positive transillumination can help with diagnosis and expedite recovery (20).
Early recognition of MLL is significant because neglected lesions can result in recurrent fluid accumulation, infection, and skin necrosis (2,39,40,49). The persistent inflammatory reaction leads to recurrent fluid accumulation and subsequent formation of a peripheral fibrous capsule that prevents reabsorption of the serosanguinous fluid (2,14). At the onset of injury, there is an accumulation of blood, lymph, debris, and necrotic fat that can potentially lead to bacterial colonization and subsequent infection (2,14,48). Hak et al. (14) showed that about half of the lesions studied were culture positive at the time of initial debridement. In addition, chronic MLL can interfere with peripheral perfusion through the dermal plexus which can lead to skin necrosis (33,41,42). Using a percutaneous technique for drainage is advantageous because it allows for preservation of this subdermal arterial plexus (48).
Nonsurgical treatment aims to evacuate the fluid between the superficial and deep fascia and prevent pseudocyst formation, infection, and skin necrosis. For acute lesions, this includes aspiration and compression. Depending on the amount of blood and lymphatic products and the acuity of the collected fluid, an aspiration with a large bore needle (e.g., 14–22 gauge) may or may not be successful (15,20,31). Like any other trauma-related fluid collection, recovery from serosanguinous type in general is shorter and less painful in comparison to a well-formed coagulated hematoma which may take a few months to completely resolve. A minimally invasive approach is advantageous because it decreases the iatrogenic injury to the remaining subcutaneous vascular supply and improves overall cosmetics (3). A Z-track method of inserting the needle in which the skin and deeper layers are not in the same plane helps seal the path (15). In athletes, aspiration allows for quicker return to play. Tejwani et al. (48) showed that repeat aspiration successfully allowed professional American football players to return to play with ultimate resolution of their lesions.
Nickerson et al. (41) has come up with a treatment algorithm for acute lesions based on their volume. They recommend observation and compression bandages for small, asymptomatic lesions less than 50 mL and percutaneous aspiration for symptomatic lesions less than 50 mL without overlying skin changes (41). They found aspirated volumes greater than 50 mL were associated with treatment failure and as a result recommend counseling patients on risk of recurrence (41). These recommendations do not include large lesions with skin necrosis which required debridement (41).
Chronic lesions that display a fibrous capsule on imaging will likely be difficult to aspirate and recur without surgical intervention (13).
The decision to proceed with surgical management still remains controversial with limited evidence-based guidelines in this clinical entity; however, several general principles may be applied to determine if and when surgical management is beneficial for patients with an MLL. Absolute indications for surgery include presence of deep infection, skin necrosis or association with an open fracture. Additionally, MLL in association with a future planned surgical procedure may benefit from early debridement and treatment because, especially in polytraumatized patients, hematoma formation may lead to bacterial colonization (14). Subacute or chronic lesions should undergo imaging as discussed previously to determine specifically the presence of a fibrous capsule, because lesions with this characteristic are likely to recur without surgical management (13).
In regard to the specifics of surgical treatment, a large incision with thorough debridement was initially recommended; however, more recent literature suggests that a more minimally invasive approach through small incisions demonstrates superior outcomes (18). Percutaneous treatment has additionally been used and has demonstrated excellent results with a quite rapid return to sport in the appropriate patient (22,31). Sclerodesis and the drain use also have been described as adjuncts to surgical debridement that may be helpful in certain clinical situations (13).
Much of the available surgical literature regarding the treatment of MLL are studies of polytrauma patients with very little mention of sports-related lower-energy mechanisms in these clinical series (16,42). Thus, it is imperative to not treat these injuries in an overly aggressive manner in the sporting population. That being said, chronic or excessively large lesions that have failed aspiration may indeed require surgical treatment which is likely to be successful when necessary (13,25,35).
Postoperative care is also of paramount importance and both drain use and strict compression of the affected area are widely regarded as critical to the success of surgical care in any MLL. Drain output should be monitored until less than 30 mL·d−1 and then discontinued, whereas compression should be consistently applied until resolution of the lesion is clinically visualized. Antibiotics have been recommended and have traditionally been used until the drain is discontinued, especially in the inpatient setting (13,16,30). Antibiotic use in the outpatient setting has not been well studied and is generally not felt necessary in the absence of a drain in the ambulatory population by the authors.
Wound vacuum-assisted closure (VAC) therapy may additionally be considered following operative management of MLL. Though emerging data has demonstrated the effectiveness of wound VAC therapy in “wounds at risk,” this adjunctive treatment has not yet been systematically evaluated in the currently available peer reviewed literature for use with MLL and thus may be used on a case-by-case basis as felt to be appropriate (17).
The exact rate of infection in patients with MLL is unknown (13). Based on limited case reports, it seems that the risk of infection is the highest postsurgical intervention followed by postaspiration/sclerotherapy and with noninvasive managements (4,13,41,49). However, cases requiring more invasive management have a higher level of acuity and are usually multitraumatic compared with cases managed conservatively. Hak et al. (14) reported that 11 of 24 cases of closed MLL of lateral hip and sacral region were culture positive during the initial debridement. However, this result has not been reproduced by other studies (4,47,49).
Fluid reaccumulation rate varies based on the size, content, location, formation of a capsule/pseudocapsule, and mechanism of injury (13,35,41,47). Nickerson et al. (41) reported that the likelihood of reaccumulation was higher in cases with aspiration of more than 50 mL of fluid compared with the cases with less than 50-mL aspiration. The presence of a fibrous capsule or pseudocapsule is a risk factor for recurrence (13). High-velocity mechanism of injury is a risk factor for recurrence (13,41).
Space-occupying MLL can compromise adjacent neurovascular structures, particularly in the extremities (5,33,46). Potential consequences include dermal necrosis, compartment syndrome, and tissue necrosis. However, none of these potential complications have been reported in sport-related MLL. Patients with any concern for neurovascular compromise should be immediately referred to an emergency department.
Regardless of the type of treatment, it is common for the soft tissue to have significant, long term bulging (Fig. 2) (36). In rare cases, chronic MLL and the consequential scar tissue formation may mimic solid neoplasms (19,24). Scars from surgical intervention and skin graft in cases of dermal necrosis may cause significant cosmetic dissatisfaction (16,25,29,42,44).
MLL is a rare but important condition that can happen as a result of sport activities. Knowledge of this diagnosis is important because delay in diagnosis can complicate its management. Careful history and physical examination is the key in the diagnosis of MLL. Musculoskeletal US and MRI remain important diagnostic modalities. Treatment varies from watchful waiting with compression wrapping to drainage and surgical intervention. In the athletic setting, timely management is the key for quick recovery and return to sport. As a result, the authors recommend prompt aspiration with a large bore needle (e.g., 14–22 gauge) in most cases with intact neurovascular adjacent tissues.
The authors declare no conflict of interest and do not have any financial disclosures.
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